Semiconductor device and a method of manufacturing the same

ABSTRACT

A semiconductor device featuring a substrate having a first surface defined by a first edge and an opposing second edge, electrode pads formed on the first surface, a first semiconductor chip mounted over the first surface between the first edge and the electrode pads and including first pads each electrically connected to a corresponding electrode pad, a second semiconductor chip stacked over the first semiconductor chip and including second pads each electrically connected to a corresponding electrode pad, a third semiconductor chip mounted over the first surface of the substrate between the second edge and the electrode pads and including third pads each electrically connected to a corresponding electrode pad, in which one electrode pad is electrically connected to one first pad, one second pad and one third pad and another electrode pad is electrically connected to a first pad and a second pad corresponding thereto, via separate bonding wires.

This application is a Continuation of U.S. application Ser. No.13/243,583, filed Sep. 23, 2011, which, in turn, is a Division of U.S.application Ser. No. 12/982,032, filed Dec. 30, 2010, now U.S. Pat. No.8,067,251, which, in turn, is a Division of U.S. application Ser. No.12/574,184, filed Oct. 6, 2009, now U.S. Pat. No. 7,879,647, which, inturn, is a Continuation of U.S. application Ser. No. 12/033,170, filedFeb. 19, 2008, now U.S. Pat. No. 7,633,146, which, in turn, is aDivision of U.S. application Ser. No. 11/392,689, filed Mar. 30, 2006,now U.S. Pat. No. 7,348,668, which, in turn, is a Continuation of U.S.application Ser. No. 10/743,882, filed Dec. 24, 2003, now U.S. Pat. No.7,061,105, which, in turn, is a Division of U.S. application Ser. No.10/194,224, filed Jul. 15, 2002, now U.S. Pat. No. 6,686,663, and which,in turn, is a Continuation of U.S. application Ser. No. 09/769,359,filed Jan. 26, 2001, now U.S. Pat. No. 6,538,331; the entire disclosuresof all of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device, and to atechnique for manufacturing the same; and, more particularly, theinvention relates to a technique which is effective when applied to asemiconductor device having a plurality of semiconductor chips stackedtherein, and which is resin-sealed in a single package.

BACKGROUND OF THE INVENTION

As one of the measures for increasing the capacity of a memory LSI, suchas a flash memory or a DRAM (dynamic random access memory), a variety ofmemory module structures, which are manufactured by stackingsemiconductor chips, each having such a memory LSI formed thereon, andthen sealing them in a single package, have been proposed.

For example, Japanese Patent Application Laid-Open No. Hei4(1992)-302164 discloses a package structure obtained by stacking,stepwise, in one package, a plurality of semiconductor chips having thesame function and the same size via an insulating layer, andelectrically connecting a bonding pad which is exposed at the steppedportion of each o f the semiconductor chips with an inner lead of thepackage through a wire.

Japanese Patent Application Laid-Open No. Hei 11(1999)-204720 disclosesa package structure manufactured by loading a first semiconductor chipon an insulating substrate via a thermocompressive sheet, loading on thefirst semiconductor chip a second semiconductor chip which is smaller inexternal size than the first semiconductor chip via anotherthermocompressive sheet, electrically connecting each of the bondingpads of the first and second semiconductor chips with an interconnectlayer on the insulating substrate via a wire, and then resin-sealing thefirst and second semiconductor chips and the wire.

SUMMARY OF THE INVENTION

If at least two semiconductor chips, which are similar in size and inthe position of a bonding pad thereof, are mounted, and the bonding padof each of the semiconductor chips is connected with an electrode of thesubstrate by a wire, it becomes difficult to detect the existence of ashort circuit between the wires in a visual inspection step conductedafter completion of the wire bonding step, because a plurality of wiresfor connecting each of the electrically common bonding pads of thesesemiconductor chips with an electrode seem to overlap when vieweddownwards from above.

Among the plurality of wires for connecting the electrically commonbonding pad with an electrode, the wire to be connected with the bondingpad of the lower semiconductor chip lies almost directly under the wireto be connected with the bonding pad of the upper semiconductor chip.Lowering the loop height of the wire to be connected with the bondingpad of the upper semiconductor chip therefore reduces the distancebetween the wire and a wire directly thereunder, which tends to cause ashort circuit between these wires. An increase in the loop height of thewire to be connected with the bonding pad of the upper semiconductorchip to prevent such a phenomenon, on the other hand, thickens the resinprovided for sealing the semiconductor chip and wire, thereby making itdifficult to reduce the thickness of the package.

An object of the present invention is to provide a technique forimproving the reliability of the visual inspection conducted after awire bonding step, in a semiconductor device having a plurality ofsemiconductor chips stacked on one another and sealed with a resin.

Another object of the present invention is to provide a technique forpromoting a size and thickness reduction of a semiconductor devicehaving a plurality of semiconductor chips stacked on one another andsealed with a resin.

A further object of the present invention is to provide a technique forreducing the manufacturing cost of a semiconductor device having aplurality of semiconductor chips stacked on one another and sealed witha resin.

The above-described and other objects and novel features of the presentinvention will be apparent from the description herein and theaccompanying drawings.

Among the features of the invention disclosed by the presentapplication, summaries of the typical aspects will next be describedbriefly.

A semiconductor device according to the present invention is obtained bymounting, over a substrate, a first semiconductor chip having aplurality of bonding pads formed along one of the sides of the mainsurface thereof; stacking, over the main surface of the firstsemiconductor chip, a second semiconductor chip having a plurality ofbonding pads formed along one of the sides of the main surface thereof;electrically connecting each of the bonding pads of the firstsemiconductor chip and each of the bonding pads of the secondsemiconductor chip with an electrode on the substrate via a wire; andsealing the first and second semiconductor chips and the wires with aresin, wherein the second semiconductor chip is stacked over the mainsurface of the first semiconductor chip while being slid (i.e., offset)in a direction parallel to said one side of the semiconductor chip andin a direction perpendicular thereto.

Another semiconductor device according to the present invention isobtained by mounting, over a substrate, a first semiconductor chiphaving a plurality of bonding pads formed along one of the sides of themain surface thereof; stacking, over the main surface of the firstsemiconductor chip, a second semiconductor chip having a plurality ofbonding pads formed along one of the sides of the main surface, whilesliding (i.e., offsetting) the second semiconductor chip in a directionparallel to said one side of the first semiconductor chip and in adirection perpendicular thereto in such a way that the one side of thesecond semiconductor chip becomes opposite to the one side of the firstsemiconductor chip and the bonding pad of the first semiconductor chipis exposed; stacking a third semiconductor chip having a plurality ofbonding pads formed along the one side of the main surface over the mainsurface of the second semiconductor chip in such a way that the one sideof the third semiconductor chip extends along the same direction withthe one side of the first semiconductor chip, and, at the same time, thethird semiconductor chip is stacked to have the same direction with thatof the first semiconductor chip; electrically connecting the bondingpads of the first, second and third semiconductor chips with electrodeson the substrate via wires; and sealing the first, second and thirdsemiconductor chips and the wires with a resin.

The manufacturing process of the semiconductor device according to thepresent invention has the following steps:

(a) mounting, over a substrate, a first semiconductor chip having aplurality of bonding pads formed along one of the sides of the mainsurface;

(b) stacking, over the main surface of the first semiconductor chip, asecond semiconductor chip having a plurality of bonding pads formedalong one of the sides of the main surface, while sliding it in adirection parallel to said one side of the first semiconductor chip andin a direction perpendicular thereto;

(c) electrically connecting, via wires, the plurality of bonding padsformed on the first and second semiconductor chips with electrodesformed on the substrate; and

(d) sealing the first and second semiconductor chips and the wires witha resin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating the outer appearance of thesemiconductor device according to one embodiment of the presentinvention;

FIG. 2 is a cross-sectional view taken along a line A-A of FIG. 1;

FIG. 3 is a plan view illustrating the base substrate of thesemiconductor device of FIG. 1;

FIG. 4( a) is a schematic plan view illustrating the connection of thebonding pads of two memory chips with the corresponding electrodes ofthe base substrate via wires by the chip stacking system according tothe present invention;

FIG. 4( b) is a schematic cross-sectional view illustrating theconnection of the bonding pads of two memory chips with thecorresponding electrodes of the base substrate via wires by the chipstacking system according to the present invention;

FIG. 5( a) is a schematic plan view illustrating the connection of thebonding pads of two memory chips with the corresponding electrodes ofthe base substrate via wires by another system;

FIG. 5( b) is a schematic cross-sectional view illustrating theconnection of the bonding pads of two memory chips with thecorresponding electrodes of the base substrate via wires by the systemof FIG. 5( a);

FIG. 6 is a cross-sectional view illustrating the semiconductor deviceaccording to another embodiment of the present invention;

FIG. 7 is a cross-sectional view illustrating the semiconductor deviceaccording to another embodiment of the present invention;

FIG. 8 is a plan view illustrating the base substrate of thesemiconductor device of FIG. 7;

FIG. 9 is a cross-sectional view illustrating the semiconductor deviceaccording to a further embodiment of the present invention;

FIG. 10 is a plan view illustrating the base substrate of thesemiconductor device of FIG. 9;

FIG. 11 is a cross-sectional view illustrating the semiconductor deviceaccording to a still further embodiment of the present invention;

FIG. 12 is a plan view illustrating the base substrate of thesemiconductor device of FIG. 11;

FIG. 13 is a cross-sectional view illustrating the semiconductor deviceaccording to a still further embodiment of the present invention;

FIG. 14 is a plan view illustrating the base substrate of thesemiconductor device of FIG. 13;

FIG. 15 is a cross-sectional view illustrating the semiconductor deviceaccording to a still further embodiment of the present invention;

FIG. 16 is a plan view illustrating the base substrate of thesemiconductor device of FIG. 15; and

FIG. 17 is a plan view illustrating the base substrate of thesemiconductor device according to a still further embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will hereinafter be described indetail based on the accompanying drawings. In all the drawings whichillustrate the embodiments of the present invention, members having alike function will be identified by like reference numerals andoverlapping descriptions thereof will be omitted.

Embodiment 1

FIG. 1 is a plan view illustrating the outer appearance of thesemiconductor device according to this Embodiment; FIG. 2 is across-sectional view taken along the longitudinal direction (a line A-A)of this semiconductor device; and FIG. 3 is a plan view illustrating thebase substrate of this semiconductor device.

The semiconductor device according to this Embodiment is a memory cardMC which is obtained by mounting, over a base substrate 2, twosemiconductor chips (which will hereinafter be called chips or memorychips) 1A having, over the main surface thereof, a flash memory formedas a semiconductor element and a semiconductor chip (which willhereinafter be called a chip or control chip) 1B having a controlcircuit for the flash memory formed thereon; sealing these three chips1A, 1A and 1B with a resin 3; and then, covering the upper surface ofthe base substrate 2 with a resin-made cap 4. This memory card MC isused for storing data, such as image data, for example, as a built-inmemory of a portable electronic apparatus, such as a digital camera. Theexternal size of the memory card MC is, for example, 32 mm on its longerside, 24 mm on its shorter side and 1.2 mm in thickness.

The two memory chips 1A mounted over the base substrate 2 of the memorycard MC have the same external size and have flash memories of the samememory capacity formed thereon. These memory chips 1A are mounted overthe base substrate 2, with one chip being stacked over the upper portionof another. The lower memory chip 1A is bonded to the upper surface ofthe base substrate 2 with an adhesive or the like, while the uppermemory chip 1A is bonded to the upper surface of the lower memory chip1A with an adhesive or the like. The control chip 1B is, on the otherhand, mounted over the base substrate 2 in the vicinity of the memorychips 1A and is bonded to the upper surface of the base substrate 2 withan adhesive or the like. These three chips 1A, 1A, 1B are each mountedover the base substrate 2 with the main surface (element formed surface)of each of them facing up.

On the main surface of each of the two memory chips 1A having a flashmemory formed thereon, a plurality of bonding pads BP are formed in aline along one side of each of the memory chips. In other words, thememory chip 1A adopts a one-side pad system, wherein bonding pads areformed at the periphery of the element surface, and, at the same time,are disposed in a line along one side of the memory chip. On the mainsurface of the control chip 1B, on the other hand, a plurality ofbonding pads BP are formed in a line along each of the two longer sidesof the chip opposite each other.

The two memory chips 1A are stacked one on another, while keeping theirdirections the same. The bonding pads BP of one memory chip 1A aredisposed in proximity to the bonding pads BP of the other memory chip1A. The upper memory chip 1A is stacked over the lower memory chip IA,while sliding them in a direction (X direction) parallel to one side ofthe lower memory chip 1A and in a direction (Y direction) perpendicularthereto, whereby a partial overlapping of the upper memory chip 1A withthe Al bonding pad BP of the lower memory chip 1A can be avoided.

On the base substrate 2 in the vicinity of the chips 1A, IA, IB, aplurality of electrodes 5 are formed, and the bonding pads of each ofthe chips 1A, IA, IB are electrically connected with the correspondingelectrodes 5 via a wire 6 made of Au (gold). The bonding pads BP of eachof the chips 1A, IA, IB are electrically connected with the connectingterminals 7B formed on one end of the main surface of the base substrate2 and test pads 8 formed on the other end via the electrodes 5 and awiring (not illustrated) of the base substrate 2 electrically connectedwith the electrodes 5. The connecting terminal 7B is used as aconnecting terminal for fitting this memory card MC to a portableelectronic apparatus and is electrically connected with an externalconnecting terminal 7A on the bottom surface of the base substrate 2 viaa through-hole 11. The test pad 8 is used for the measurement ofelectrical properties, such as, for example, in a fabrication step ofthis memory card MC.

FIG. 4( a) is a schematic plan view illustrating the state of connectionof the bonding pads BP of each of the two memory chips 1A with thecorresponding electrodes 5 of the base substrate 2 via wires 6; and FIG.4( b) is a cross-sectional view thereof.

As described above, the memory chips 1A are stacked in two layers andthe upper memory chip 1A is stacked over the lower memory chip 1A, whilesliding the upper memory chip 1A, in the X direction parallel to oneside of the lower memory chip 1A and in the Y direction perpendicularthereto. When the electrically common bonding pads BP (for example, thebonding pad BPa of the upper memory chip 1A and the bonding pad BPb ofthe lower memory chip 1A) of the two memory chips 1A and thecorresponding electrode 5 are connected through two wires 6 (forexample, the wire 6 a and wire 6 b), the wire 6 a connected with one ofthe bonding pads BPa does not overlap with the wire 6B connected withthe other bonding pad BPb when viewed from above. In this case, it istherefore possible to easily examine the state of connection of thewires 6 and detect, for example, the existence of a short circuitbetween the upper and lower wires 6 by viewing downwards, through acamera, the base substrate 2 in a visual inspection step conducted aftercompletion of the wire bonding step.

When the upper memory chip 1A is stacked over the lower memory chip 1Awhile sliding the upper memory chip 1A only in one direction (forexample, X direction), the wire 6 a connected with the bonding pad ofone of the memory chips 1A seems to overlap with the wire 6 b connectedwith the other memory chip 1A when viewed from above, which makes itdifficult to visually detect the existence of a short circuit betweenthe upper and lower wires 6.

In the above-described stacking system, as illustrated in FIGS. 5( a)and 5(b), the wire 6 b connected with the bonding pad BPb of the lowermemory chip 1A lies almost right under the wire 6 a connected with thebonding pad BPa of the upper memory chip 1A, so that lowering the loopheight of the wire 6 a reduces the distance with the wire 6 b lyingdirectly thereunder, tending to cause short circuit therebetween.

Since, in the chip stacking system of FIG. 4( a) according to thisEmbodiment, the wire 6 a and the wire 6 b connected with the sameelectrode 5 are slid in a horizontal direction, lowering the loop heightof the wire 6 a is not likely to cause a short circuit with the wire 6b, which lies under the wire 6 a. In other words, adoption of the chipstacking system according to this Embodiment makes it possible to lowerthe loop height of the wire 6 connected with the bonding pad BP of theupper memory chip 1A, thereby decreasing the thickness of the resin forsealing the chips 1A, IA, 1B and the wire 6, leading to a thickness andweight reduction of the resulting memory card MC.

The memory card MC of this Embodiment, having the structure as describedabove, can be fabricated as follows. First, a first memory chip 1A ismounted over a base substrate 2 using an adhesive or the like, followedby stacking a second memory chip 1A over the upper surface of the firstmemory chip 1A using an adhesive or the like, while sliding the secondmemory chip 1A in each of X and Y directions relative to the firstmemory chip 1A. Almost simultaneously with the stacking work, a controlchip 1B is mounted using an adhesive or the like over the other regionof the base substrate 2.

Next, the base substrate 2, having the chips 1A, IA, IB mountedthereover, is loaded on a heating stage of a wire bonding apparatus.After the reverse side of the base substrate 2 is fixed at the heatingstage by vacuum adsorption or the like, the bonding pads BP of the chips1A, IA, IB and corresponding electrodes 5 are electrically connectedsuccessively with a wire 6. For the connection via the wire 6, a wirebonding method using thermo compression bonding and supersonic vibrationin combination is employed. Upon connection of the bonding pad BP of theupper memory chip 1A with the electrode 5 via the wire 6, the loopheight of the wire 6 to be connected with the bonding pad BP of theupper memory chip 1A can be lowered more by adopting a reverse bondingsystem, wherein bonding (first bonding) of one end of the wire 6 to thesurface of the electrode 5 is followed by bonding (second bonding) ofthe other end of the wire 6 to the surface of the bonding pad BP.

After determination of the connected state of the wire 6 by visualinspection, the chips 1A, IA, IB and wire 6 are sealed with a resin 3.Sealing may be conducted with either one of a potting resin or a moldingresin. Electrical properties are then tested by bringing a probe intocontact with the test pad 8 formed on one end of the base substrate 2.The upper surface of the base substrate 2 is covered with a resin-madecap 4, whereby the memory card MC according to this Embodiment asillustrated in FIGS. 1 to 3 is completed.

In order to reduce the manufacturing cost by decreasing the number ofparts which make up the memory card, the whole upper surface of the basesubstrate 2 may be sealed with the resin 3, as illustrated in FIG. 6,instead of covering the upper surface of the base substrate 2 with thecap 4. Upon resin sealing, either single substrate sealing or multiplesubstrate sealing may be adopted.

The above-described memory card MC has the control chip 1B mounted overthe base substrate 2, but it is possible to stack the control chip 1 B,which is smaller in external size than the memory chip 1A, over theupper surface of the upper memory chip 1A, as illustrated in FIGS. 7 and8.

Adoption of such a chip stacking system makes it possible to decreasethe external size of the base substrate 2, because a separate region ofthe base substrate 2 to mount the control chip 1B thereon becomesunnecessary, leading to a reduction in the size and weight of the memorycard MC.

In such a chip stacking system, however, the chips 1A, IA, IB arestacked in three layers, which increases the thickness of the resin forsealing the chips 1A, IA, IB and wire 6, thereby preventing a reductionof the thickness of the memory card MC. As a countermeasure, an increasein the thickness of the resin 3 can be suppressed by polishing thereverse side of each of the chips 1A, IA, IB, thereby decreasing theirthicknesses.

The chip stacking system according to this Embodiment can also beapplied to a package like a BGA (ball grid array) type package. The BGAas illustrated in FIGS. 9 and 10 is obtained, for example, by using aresin 3 to seal the whole upper surface of a base substrate 2 havingthereon two memory chips 1A, stacked in respective layers, and a controlchip 1B, and by connecting, via the bottom surface of the base substrate2, a bump electrode 10 made of solder or the like. The BGA asillustrated in FIGS. 11 and 12 is obtained by stacking the control chip1B over the two memory chips 1A, which are stacked in respective layers.

When the chip stacking system of this Embodiment is applied to a BGA,the thermal stress applied to the bump electrode 10 upon mounting of theBGA to the substrate can be reduced by interposing, between the lowermemory chip 1A and base substrate 2, a sheet material made of anelastomer or, porous resin which has a lower modulus of elasticity thanthe resin material forming the base substrate 2.

Embodiment 2

FIG. 13 is a cross-sectional view illustrating the semiconductor deviceof this Embodiment, while FIG. 14 is a plan view illustrating the basesubstrate of this semiconductor device.

The semiconductor device of this Embodiment is a memory card MC obtainedby mounting over a base substrate 2 four memory chips 1A₁ to 1A₄, eachhaving a flash memory formed thereon, and a control chip 1B; sealingthese chips 1A₁ to IA₄ and 1B with a resin 3; and covering the uppersurface of the base substrate 2 with a resin cap 4.

The four memory chips 1A₁ to 1A₄ have the same external size and have aflash memory of the same memory capacity formed thereon. These memorychips 1A₁ to 1A₄ each have a single-side pad system wherein bonding padsBP are formed at the periphery of the element surface, and they arearranged in a line along one of the sides of each of the memory chips.

In this Embodiment, these four memory chips 1A₁ to 1A₄ are mounted overthe base substrate 2, while being stacked in four layers. In this case,the second memory chip 1A₂ and fourth memory chip 1A₄ are stackedrelative to the first memory chip 1A₁ and the third memory chip 1A₃,respectively, while sliding the former ones in a direction (X direction)parallel to the one side along which bonding pads BP are arranged and ina direction (Y direction) perpendicular thereto. The memory chips 1A₁ to1A₄, are stacked one on another with their faces turned in the samedirection. The memory chips 1A₁ and 1A₃, as well as the memory chips 1A₂and 1A₄, are stacked one after another so that the upper one lies rightabove the lower one when viewed from above. The second memory chip 1A₂and the top memory chip 1A₄ are oriented relative to the bottom memorychip 1A₁ and the third memory chip 1A₃, respectively, so that theposition of the bonding pads BP are reversed, that is, right side left.

In the above-described chip stacking system according to thisEmbodiment, no horizontal sliding occurs between the wires 6 of thebottom memory chip 1A₁ and the third memory chip 1A₃, and also betweenthe two wires 6 of the second memory chip 1A₂ and the outermost memorychip 1A₄, but existence of another memory chip between the memory chips1A₁ and 1A₃, or 1A₂ and 1A₄ makes it possible to conduct wire bondingwithout giving any consideration to the wire loop.

Accordingly, the upper and lower wires 6 to be bonded on the same sidebecome free from a short-circuit problem, so that the state ofconnection of the wire 6 can be judged easily using a camera or the likein a visual inspection step conducted after the completion of the wirebonding step.

As illustrated in FIGS. 15 and 16, the chip stacking system according tothis Embodiment can be applied, similar to the chip stacking system ofEmbodiment 1, to a resin-sealed type package, such as one using a BGA.It is needless to say that, as in Embodiment 1, a control chip 1Bsmaller in external size than the outermost memory chip 1A₄ can bestacked over the upper surface thereof.

As illustrated in FIG. 17, bonding pads BP (signal pins) common to eachof the two memory chips 1A and control chip 1B may be connected with thesame electrode 5 on the base substrate 2. FIG. 17 illustrates an exampleof application of such a structure to a memory card MC. It is needlessto say that such a structure can be applied to a BGA type package aswell.

The invention made by the present inventors so far has been describedspecifically based on some Embodiments. It should however be borne inmind that the present invention is not limited to or by theseEmbodiments and can be modified within an extent not departing from thescope of the present invention.

In the above-described Embodiments, a description was made concerningthe stacking of chips, each having a flash memory formed thereon. Thoseembodiments are not limited to such a construction, but can also beapplied to stacking of a plurality of chips which are different inexternal size or in the kind of a memory formed thereon.

In the above-described Embodiments, a description was made concerningthe stacking of two or four memory chips. Those embodiments are notlimited thereto, but can also provide for the stacking of three chips,as well as at least five chips.

Advantages available from the typical inventive features disclosed bythe present application will next be described.

The present invention makes it possible, in a semiconductor deviceobtained by stacking a plurality of semiconductor chips, and thensealing the chips with a resin, to reduce the occurrence of a shortcircuit between the wires connected with the bonding pad of the lowersemiconductor chip and that of the upper semiconductor chip.

The present invention makes it possible, in a semiconductor deviceobtained by stacking a plurality of semiconductor chips, and thensealing the chips with a resin, to improve the reliability of the visualinspection conducted after the wire bonding step.

The present invention makes it possible to promote a size and thicknessreduction of a semiconductor device obtained by stacking a plurality ofsemiconductor chips, and then sealing the chips with a resin.

The present invention facilitates the stacking of a plurality ofsemiconductor chips, thereby making it possible to realize asmall-sized, thin and large-capacity memory package.

The present invention makes it possible, in a semiconductor deviceobtained by stacking a plurality of semiconductor chips, and thensealing the chips with a resin, to reduce the manufacturing cost of thesemiconductor device, because the semiconductor chip and the substratecan be electrically connected by a wire bonding system.

1. A semiconductor device comprising: a substrate including a firstsurface that is defined by a first edge and a second edge opposed to thefirst edge; a first electrode pad formed on the first surface of thesubstrate; a first semiconductor chip including a first pad thereon, andmounted over the first surface of the substrate, the first semiconductorchip being positioned between the first edge and the first electrodepad; a second semiconductor chip including a second pad thereon, andstacked over the first semiconductor chip; and a third semiconductorchip including a third pad thereon, and mounted over the first surface,the third semiconductor chip being positioned between the second edgeand the first electrode pad, wherein the first electrode pad iselectrically connected to the first, second and third pads.
 2. Thesemiconductor device according to claim 1, further comprising: a firstbonding wire electrically connecting the first pad of the firstsemiconductor chip to the first electrode pad; a second bonding wireelectrically connecting the second pad of the second semiconductor chipto the first electrode pad; and a third bonding wire electricallyconnecting the third pad of the third semiconductor chip to the firstelectrode pad, wherein the first electrode pad is electrically connectedto the first, second and third pads by the first, second and thirdbonding wires.
 3. The semiconductor device according to claim 2, whereinone of the first, second and third bonding wires is electricallyconnected to the first electrode pad of the substrate by a reversebonding, the other of the first, second and third bonding wires areelectrically connected to the first electrode pad of the substrate by aforward bonding.
 4. The semiconductor device according to claim 1,further comprising: a second electrode pad formed on the first surfaceof the substrate, the second electrode pad being positioned between thefirst semiconductor chip and the third semiconductor chip, wherein thefirst semiconductor chip includes a fourth pad thereon, the secondsemiconductor chip includes a fifth pad thereon, and the secondelectrode pad is electrically connected to the fourth and fifth padswithout connecting the third semiconductor chip.
 5. The semiconductordevice according to claim 4, wherein the first and second electrode padsare disposed along a line that is substantially parallel to the firstedge of the substrate.
 6. The semiconductor device according to claim 4,further comprising: third, fourth and fifth electrode pads formed on thefirst surface of the substrate, the third, fourth and fifth electrodepads being positioned between the first semiconductor chip and the thirdsemiconductor chip, wherein the first semiconductor chip includes asixth pad thereon, the second semiconductor chip includes a seventh padthereon, the third semiconductor chip includes a eighth pad thereon, thethird electrode pad is electrically connected to the sixth pad of thefirst semiconductor chip without connecting the second semiconductorchip and the third semiconductor chip, the fourth electrode pad iselectrically connected to the seventh pad of the second semiconductorchip without connecting the first semiconductor chip and the thirdsemiconductor chip, and the fifth electrode pad is electricallyconnected to the eighth pad of the third semiconductor chip withoutconnecting the first and second semiconductor chips.
 7. Thesemiconductor device according to claim 1, wherein each of the firstsemiconductor chip and the second semiconductor chip is a memory chip,and the third semiconductor chip is a control chip.
 8. The semiconductordevice according to claim 1, wherein the second semiconductor chip isdeviated from the first semiconductor chip toward the first edge of thesubstrate so that the first pad of the first semiconductor chip isexposed.
 9. A semiconductor device comprising: a substrate including afirst surface and a plurality of electrode pads formed on the firstsurface, the first surface including a first side and a second sideopposed to the first side; a first semiconductor chip including a mainsurface and a plurality of first pads formed along one side of the mainsurface, and mounted over the first surface of the substrate, the firstsemiconductor chip disposed between the first side and the electrodepads so that the one side of the first semiconductor chip faces theelectrode pads; a second semiconductor chip including a main surface anda plurality of second pads formed along one side of the main surface,and stacked over the main surface of the first semiconductor chip sothat the one side of the second semiconductor chip faces the electrodepads; a third semiconductor chip including a main surface and aplurality of third pads formed along one side of the main surface, thethird semiconductor chip disposed between the second side and theelectrode pads so that the one side of the third semiconductor chipfaces the electrode pads; a plurality of first bonding wireselectrically connecting the first pads of the first semiconductor chipto electrode pads of the substrate, respectively; a plurality of secondbonding wires electrically connecting the second pads of the secondsemiconductor chip to the electrode pads of the substrate, respectively;and a plurality of third bonding wires electrically connecting the thirdpads of the third semiconductor chip to the electrode pads of thesubstrate, respectively, wherein the plurality of electrode pads includea first common electrode pad, the first common electrode pad iselectrically connected to a corresponding one of the first bondingwires, a corresponding one of the second bonding wires and acorresponding one of the third bonding wires.
 10. The semiconductordevice according to claim 9, wherein the plurality of electrode padsinclude a second common electrode pad, the second common electrode padis electrically connected to a corresponding one of the first bondingwires and a corresponding one of the second bonding wires withoutconnecting the third bonding wires.
 11. The semiconductor deviceaccording to claim 9, wherein each of the first semiconductor chip andthe second semiconductor chip is a memory chip, and the thirdsemiconductor chip is a control chip.
 12. The semiconductor deviceaccording to claim 9, wherein the second semiconductor chip is deviatedfrom the first semiconductor chip toward the first side of the substrateso that the first pads of the first semiconductor chip are exposed. 13.The semiconductor device according to claim 9, wherein one of the first,second and third bonding wires is electrically connected tocorresponding one of the electrode pads of the substrate by a reversebonding, the other of the first, second and third bonding wires areelectrically connected to corresponding one of the electrode pads of thesubstrate by a forward bonding.
 14. The semiconductor device accordingto claim 9, wherein the plurality of electrode pads are disposed along aline that is substantially parallel to the first side of the substrate.15. The semiconductor device according to claim 9, wherein the firstcommon electrode pad is larger in size than another of the electrodepads of the substrate.
 16. A semiconductor device comprising: asubstrate including a first surface and a plurality of electrode padsformed on the first surface, and the plurality of electrode padsincluding a first common electrode pad; a first memory chip, a secondmemory chip and a control chip provided over the first surface, each ofthe first memory chip, the second memory chip and the control chipincluding a main surface and a plurality of bonding pads formed on themain surface, respectively; a first bonding wire electrically connectinga selected one of the bonding pads of the first memory chip to the firstcommon electrode pad of the substrate; a second bonding wireelectrically connecting a selected one of the bonding pads of the secondmemory chip to the first common electrode pad of the substrate; and athird bonding wire electrically connecting a selected one of the bondingpads of the control chip to the first common electrode pad of thesubstrate.
 17. The semiconductor device according to claim 16, whereinthe plurality of electrode pads include a second common electrode pad,and the semiconductor device further comprising: a fourth bonding wireelectrically connecting another of the bonding pads of the first memorychip to the second common electrode pad of the substrate; and a fifthbonding wire electrically connecting another of the bonding pads of thesecond memory chip to the second common electrode pad of the substrate,wherein the second common electrode pad is electrically connected to thefirst and second memory chips via the fourth and fifth bonding wireswithout connecting the control chip.
 18. The semiconductor deviceaccording to claim 16, wherein the first surface of substrate includes afirst side and a second side opposed to the first side, the first memorychip is mounted over the first surface of the substrate so as to bedisposed between the first side and the electrode pads, the secondmemory chip is stacked over the first memory chip, and the control chipis mounted over the first surface of the substrate so as to be disposedbetween the second side and the electrode pads.
 19. The semiconductordevice according to claim 16, wherein the second memory chip is deviatedfrom the first memory chip toward the first side of the substrate sothat the bonding pads of the first memory chip are exposed.
 20. Thesemiconductor device according to claim 16, wherein one of the first,second and third bonding wires is electrically connected tocorresponding one of the electrode pads of the substrate by a reversebonding, the other of the first, second and third bonding wires areelectrically connected to corresponding one of the electrode pads of thesubstrate by a forward bonding.